9 February 2015

PLUTO: UK RAF FMCW OTH Radar

The British Royal Airforce is operating the so-named PLUTO OTH Radar in their base in Akrotiri, Cyprus. It is often on 10, 21 and 28 MHz HAM bands with sweeprates of 25 and 50sweeps/sec, sometimes 12.5sweeps/sec.

Below, the radar heard on 8070.0 Khz, 20 Khz bandwidth but with a sweep-rate of 25 sps:

OTH
radars can detect and track aircraft, missiles in the atmosphere, and
even large ships within the coverage fan as long as the objects are at
least 500-1000 km from the radar and no more than about 5000 km, with
the best coverage in the 1000-3500 km range.The
area covered by such radars is usually a fan extending in a line
perpendicular to the transmitter array and as much as 50 degrees to
either side, for a total fan width of up to 100 degrees. Although some
OTH radars have a much narrower fan (ca 60 degrees), the alignment of
the receiver arrays at Agios Nikolaos suggests that this system does have a wide fan.

PLUTO transmitter SITE, north From Akrotiri (Cyprus)

This image shows approximately what the fan for the Pluto radar might look like, assuming that it is as wide as estimated above. The concentric arcs are at 1000 km intervals and the radiating lines are at 10 degree intervals. As can be seen, the fan covers little or none of Syria, Lebanon, Jordan, and Israel, but provides good coverage of Iraq, Iran, the Gulf States, part of Saudi Arabia, and most of Afghanistan, Pakistan, and the former Soviet Stans, and possible coverage of part of India. The Russian launch areas at Baikonur and Kapustin Yar are probably covered, as is the Persian Gulf and much of the Arabian Sea.

The receiver element, typically one or more long, linear arrays of antennas, is usually somewhat distant from the transmit site, as much as 100 km. In the case of this system, the receivers are likely to be at the other British Sovereign Base Area, Agios Nikolaos. There are three long white rectangular areas visible in the low-res GE imagery of Agios Nikolaos that might be the system's receive arrays.